It isn't hard to learn to recognize the signs of lying in a young child. The key is to look for signs of nervousness, which are usually easy enough to see — as long as you know what you're looking for. The important thing here is to know what's normal and what's not for your own child. If he has a habit of blinking excessively all the time, for example, then you can't take his fluttering eyelashes into consideration when you're trying to determine whether his words are true or false.